Sodium metal batteries with intercalating cathode

Abstract

Cell and batteries containing them employing a cathode having a intercalating metal oxide in combination with a sodium metal haloaluminate. At operating temperatures, the positive electrode (cathode) of the invention comprises electroactive cathode material permeated with and in physical and electrical contact with the sodium metal haloaluminate catholyte. The positive and negative electrodes are separated with a solid alkali metal conducting electrolyte. The intercalating metal oxice is not in direct physical contact with the solid electrolyte. Electric and ionic conductivity between the solid electrolyte and the positive electrode is mediated by the sodium haloaluminate catholyte. Batteries of the invention are useful for bulk energy storage, particularly for electric utility grid storage, as well as for electric vehicle propulsion.

The invention claimed is: 
     
       1. A storage cell comprising:
 a negative electrode comprising molten sodium metal; 
 a positive electrode having a solid sodium-intercalating metal oxide as the active cathode material; 
 a molten sodium haloaluminate catholyte; and 
 a solid sodium-conducting separation element intermediate between the negative electrode and the molten sodium haloaluminate catholyte; 
 wherein the molten sodium haloaluminate catholyte permeates the solid metal oxide of the positive electrode, and 
 wherein the sodium intercalating metal oxide is γ-Fe 2 O 3 . 
 
     
     
       2. The cell of  claim 1 , wherein the sodium intercalating metal oxide is retained in the cell in a conductive container or receptacle, permeable to the molten catholyte, such that contact of the sodium intercalating metal oxide with the separation element is avoided. 
     
     
       3. The cell of  claim 1 , wherein the catholyte is sodium chloroaluminate. 
     
     
       4. The cell of  claim 1 , wherein the catholyte is NaAlCl 4 . 
     
     
       5. The cell of  claim 1 , wherein the positive electrode further comprises an electronically conductive material dispersed in the positive electrode. 
     
     
       6. A rechargeable battery comprising a plurality of cells of  claim 1 . 
     
     
       7. A method for generating energy, comprising forming one or more cells of  claim 1  and discharging the one or more cells, wherein the one or more cells is operated at a temperature ranging from 150° C. to 320° C. 
     
     
       8. The method of  claim 7  further comprising a step of storing electrical energy wherein the one or more cells are rechargeable and wherein after discharge the one or more cells are recharged by application of a voltage to the cell. 
     
     
       9. A method for storing energy, comprising forming one or more cells of  claim 1  and charging the one or more cells, wherein the one or more cells is operated at a temperature ranging from 150° C. to 320° C. 
     
     
       10. The cell of  claim 2 , wherein the receptacle is a metal mesh. 
     
     
       11. The cell of  claim 5 , wherein the dispersed electronically conductive material is carbon particles. 
     
     
       12. The cell of  claim 5 , wherein the dispersed electronically conductive material is selected from carbon black, active carbon, acetylene black, graphite fine particles, carbon fibers, SiC, Ti 3 SiC 2 , WC, Nb 0.1 Ti 0.9 O 2 , TaC, TaC 0.75  and TaC 0.5 . 
     
     
       13. The cell of  claim 1  which is operated at a temperature ranging from 150° C. to 320° C. 
     
     
       14. The cell of  claim 1  which is operated at a temperature ranging from 200° C. to 300° C. 
     
     
       15. The cell of  claim 1 , wherein the positive electrode consists of γ-Fe 2 O 3  permeated with the molten sodium haloaluminate catholyte. 
     
     
       16. The cell of  claim 1 , wherein the positive electrode consists of γ-Fe 2 O 3  permeated with the molten sodium haloaluminate catholyte and a dispersed electronically conductive material. 
     
     
       17. The cell of  claim 15  which is operated at a temperature ranging from 150° C. to 320° C. 
     
     
       18. The cell of  claim 15  which is operated at a temperature ranging from 200° C. to 300° C. 
     
     
       19. The method of  claim 7 , wherein the cell is operated at a temperature ranging from 200° C. to 300° C. 
     
     
       20. The method of  claim 9 , wherein the cell is operated at a temperature ranging from 200° C. to 300° C. 
     
     
       21. The cell of  claim 16 , wherein the dispersed electronically conductive material is carbon particles. 
     
     
       22. The cell of  claim 16 , wherein the dispersed electronically conductive material is selected from the group consisting of carbon black, active carbon, acetylene black, graphite fine particles, carbon fibers, SiC, Ti 3 SiC 2 , WC, Nb 0.1 Ti 0.9 O 2 , TaC, TaC 0.75  and TaC 0.5 . 
     
     
       23. A storage cell comprising:
 a negative electrode comprising molten sodium metal; 
 a positive electrode having a solid sodium-intercalating metal oxide as the active cathode material; 
 a molten sodium haloaluminate catholyte, which is sodium chloroaluminate; and 
 a solid sodium-conducting separation element intermediate between the negative electrode and the molten sodium chloroaluminate; 
 wherein the positive electrode consists of γ-Fe 2 O 3  permeated with molten sodium chloroaluminate and a dispersed electronically conductive material; and 
 wherein the solid sodium-conducting separation element is β″-alumina. 
 
     
     
       24. A method for generating energy, comprising forming one or more cells of  claim 23  and discharging the one or more cells, wherein the one or more cells is operated at a temperature ranging from 150° C. to 320° C.